EMF and Voltammetric Measurements on the U(IV)/U(III) Couple in Molten LiF-BeF[sub 2]-ZrF[sub 4]

Abstract

mentioning that the mechanism suggested by Breck and Lin is sufficiently similar to the mechanism of H + transport under an electric field, i.e., considering the transport of H + as a sort of "structural diffusion." In view of the fact that in these two cases the driving forces involved are quite different, this is an interesting thing to know. An electric field (for example a d-c field) will tend to align the solvent dipole and thus create more order, whereas a temperature gradient would tend to create more disorder by way of setting up a thermal energy gradient among the solvent molecules.To evaluate the ionic entropy of transport on an "absolute" basis, a study of the problem of standard state is necessary. We plan to discuss this subject in a forthcoming article.

Dynamic Reference Electrode development for redox potential measurements in fluoride molten salt at high temperature

“…Boron nitride (BN), which is normally an insulator in fluoride melt, has been used. It is slowly impregnated by the melt to provide ionic contact [14][15][16]. In these conditions a compartment of BN is filled with the molten salt containing generally NiF 2 and a Ni wire ensuring the electrical contact.…”

Electrochemical Studies of Uranium and Thorium in Molten LiF-NaF-KF at 500°C

“…In this paper we describe electrochemical studies of uranium(IV) and thorium(IV) in a basic fluoride solvent L~F-NaF-KF [46. 5-11.5-42.0 m/o (mole per cent) ] at 500~ Electrochemical studies of uranium in other molten fluorides have been described (1)(2)(3)(4) and the results of these investigations have been summarized by one of us (5). The U(IV) reduction in the more acidic LiF-BeF~-ZrF4 (65.6-29.4-5.0 m/o) at 500~ was shown (1,2) to be a reversible, one-electron process occurring at -,, --1.5V (vs. the unit mole fraction Ni(II)/Ni couple).…”

“…5-11.5-42.0 m/o (mole per cent) ] at 500~ Electrochemical studies of uranium in other molten fluorides have been described (1)(2)(3)(4) and the results of these investigations have been summarized by one of us (5). The U(IV) reduction in the more acidic LiF-BeF~-ZrF4 (65.6-29.4-5.0 m/o) at 500~ was shown (1,2) to be a reversible, one-electron process occurring at -,, --1.5V (vs. the unit mole fraction Ni(II)/Ni couple). No voltammetric reduction wave for U(III) was observed at platinum prior to the cathodic limit of the melt.…”

Lanthanum Trifluoride as a Membrane in a Reference Electrode for Use in Certain Molten Fluorides

“…The melt contained approximately 0.2 m/o UF4. The concentration of U(III) was varied by controlled reduction of U(IV) with zirconium metal (13). Of interest here was to observe if an increase in the concentration of U(III) (melt more reducing) would adversely affect the performance of the reference electrode which would be reflected in erratic half-wave potentials.…”